In SDH networks and SONET networks, the scope of the network management correlates tasks with the number of channels transmitted simultaneously (SDH=synchronous digital hierarchy and SONET=synchronous optical network). The more channels that are transmitted, the more tasks have to be carried out. The tasks include, for example, configuration, administration, maintenance and supervision. Owing to the ever-increasing requirement for data transmission, the available number of transmission channels in the backbone network increase continuously.
One of the primary functions in a SONET SDH ring is the addition and deletion of circuits at each of the add-drop multiplexers (ADMs) that constitute the ring. This function is generally performed by the cross connect or switch fabric that is central to the ADM. The cross connect fabric will generally receive frame aligned data from each of the optical or electrical interfaces present on the ADM. Assuming that the switch follows a TSI (Time slot interchanger) architecture, depending on the configuration of the ADM, the time stage of the fabric cross connects the data from a given time slot in the incoming data stream to a time slot in any of the outgoing data streams. This necessitates the configuration of the time stage of the cross connect on a per time slot basis.
A typical STM-1 SDH ADM has the following components as shown in FIG. 1.    a) one STM1 east interface and the associated processing functions (100)    b) one STM1 west interface and the associated processing functions (101)    c) 63 E1 or 84 DS1 interfaces and the associated mapping functions (102)    d) 3 E3 interfaces and the associated mapping functions (103)    e) “time stage only” switch including the frame reference and address generation function (104).
Each of the interface blocks 100, 101, 102 and 103 pump data towards the central switch fabric 104 at STM1 rate over the links 105, 106, 107 and 108. Thus for the ADM to be able to cross connect any of the byte in the coming frame to any of the byte in the outgoing frame, one need to store at least    a) (270×9) bytes of telecom data per interface    b) (270×9) words of configuration information per interface.
In a typical SDH ADM generally it is not required to switch data on a byte level, but only at a TU12 or TU11 level. Further, assuming that all the interface blocks 100, 101, 102 and 103 pump data towards the central switch fabric 104 with their frames aligned and the J1 bytes aligned, the data in a given column of the incoming SDH frame would correspond to the same TU12 or TU11 or TU3 irrespective of the row it is in. Hence it is required to store only    a) 270 bytes of telecom data per interface    b) 270 words of configuration information per interface
Further assuming that the data coming towards the central switch fabric 104 on links 105, 106 and 107 contain only TU12s or TU11s, then one can further reduce the amount of storage and configuration information required as follows    1) If the incoming data stream contains only TU12s, then we are required to store at least
(a) 63 bytes of telecom data per interface
(b) 63 words of connection information per interface.
This is because in an SDH frame, the same TU12 number repeats after 63 columns    2) If the incoming data stream contains only TU11s, then we are required to store at least
(a) 84 bytes of telecom data per interface
(b) 84 words of connection information per interface.
This is because in an SDH frame, the same TU11 number repeats after 84 columns.
However there would be a problem in storing the telecom data and the connection information if the incoming data stream contains a mix of TU11 and TU12. Existing techniques solve the problem of switching TU11 and TU12 simultaneously by making the fabric, switch at a column level (essentially column level switch). Since all the bytes for any TU12 falls in fixed four columns and all the bytes for a TU11 falls in fixed three columns this is a viable solution. However this scheme needs more storage (ideally we need to store only 1 of the 4 bytes of TU12 in a row and 1 of the 3 bytes of TU 11 in row).
Therefore, there is a need to overcome the above restriction or problem which has an effective and efficient method and apparatus for reducing the resource utilization of the switching fabric in a SONET/SDH Multiplexer instead of byte or column level.